1. Technical Field
This invention relates to a reformer in which fuel gas (raw material gas) is reformed to product gas and supplied to anodes (fuel electrodes) of cells in fuel cell systems, in particular, relates to a plate type reformer in which reforming reaction is conducted while the fuel gas is indirectly heated by burning gas which is supplied to cathodes (air electrodes) of the cells.
2. Background Art
A fuel cell system is an electricity generating system using reversed electro-chemical reaction of an electrolysis of water in electrolytes including carbonates, phosphates, etc. with hydrogen gas being supplied to an anodes (fuel electrodes) and buring gas (O.sub.2, CO.sub.2) to a cathodes (air electrodes) in the cells.
The hydrogen gas, which is supplied to the anode, is obtained by supplying fuel gas, such as methane as raw material gas with steam to the reformer, in accordance with reforming reaction which is given by the following chemical equations with use of catalysts. EQU CH.sub.4 +H.sub.2 O.fwdarw.CO+3H.sub.2 EQU CO+H.sub.2 O.fwdarw.CO.sub.2 +H.sub.2
To maintain reforming temperature in the reformer, remaining hydrogen or carbon monoxide in the anode gas is supplied into the reformer and burned there to heat up indirectly the fuel gas to be reformed.
In such a reformer, however, air and fuel flow into a combustor of the reformer to be burned together, so that volume of the combustor has to be large, and the reformer is often too large in size. Temperature of burned gas was as high as 1300 degrees C. until heat was transferred to the reforming gas and it is structurally impossible to decrease temperature of the burnt gas in order to match temperature of heat receiving gas (between 550 and 750 degrees C.).
To solve these problems, plate type reformers which are compact in size, and in which uniform combustion all over the combustor is possible to achieve effective reforming were recently proposed (for example, Japanese Patent Application Laid Open No. Sho. 62-160136 (160136/1987).